Luminescent diazabenzimidazole carbene metal complexes

1. A metal-carbene complex of the Formula (I):

wherein:

M is Ir;

m is 1, 2, or 3;

o is 0, 1, or 2; and

the sum of m and o is 3;

with the proviso that, if o is 2, the ligands L may be the same or different;

L is a monoanionic bidentate ligand of formaula (A),(B),or(C):

wherein in formula (A):

R 51 is in each case independently a linear or branched C 1 -C 8 alkyl group; a substituted or unsubstituted C 6 -C 18 aryl radical; or a substituted or unsubstituted C 6 -C 12 heteroaryl; and

R 52 is hydrogen; a linear or branched C 1 -C 6 alkyl group; or a substituted or unsubstituted C 6 -C 18 aryl radical;

wherein each substituent is independently a C 1 -C 8 alkyl group;

wherein in formula (B):

A 9′ is CR 12′ or N;

A 10′ is CR 13′ or N;

R 11′ is a linear or branched, substituted or unsubstituted alkyl radical having 1 to 20 carbon atoms, optionally interrupted by at least one heteroatom selected from O, S and N; a substituted or unsubstituted cycloalkyl radical having 3 to 18 carbon atoms; a substituted or unsubstituted heterocycloalkyl radical interrupted by at least one heteroatom selected from O, S and N, and having 3 to 18 carbon atoms and/or heteroatoms; a substituted or unsubstituted aryl radical having 6 to 30 carbon atoms; or a substituted or unsubstituted heteroaryl radical interrupted by at least one heteroatom selected from O, S and N and having a total of 5 to 30 carbon atoms and/or heteroatoms;

R 12′ and R 13′ are each independently hydrogen; deuterium; a linear or branched, substituted or unsubstituted alkyl radical having 1 to 20 carbon atoms, optionally interrupted by at least one heteroatom selected from O, S and N; a substituted or unsubstituted cycloalkyl radical having 3 to 18 carbon atoms; a substituted or unsubstituted heterocycloalkyl radical interrupted by at least one heteroatom selected from O, S and N, and having 3 to 18 carbon atoms and/or heteroatoms; or a substituted or unsubstituted aryl radical having 6 to 30 carbon atoms; a substituted or unsubstituted heteroaryl radical interrupted by at least one heteroatom selected from O, S and N and having a total of 5 to 30 carbon atoms and/or heteroatoms;

if A 9′ is CR 12′ and A 10′ is CR 13′ , CR 12′ and CR 13′ together may form, a saturated, unsaturated, or aromatic, optionally substituted ring, which is optionally interrupted by at least one heteroatom selected from O, S and N, has a total of from 5 to 18 carbon atoms and/or heteroatoms, and may optionally be fused to at least one further optionally substituted saturated, unsaturated, or aromatic ring, optionally interrupted by at least one heteroatom selected from O, S and N, and having a total of from 5 to 18 carbon atoms and/or heteroatoms;

A 5′ is CR 14′ or N;

A 6′ is CR 15′ or N;

A 7′ is CR 16′ or N;

A 8′ is CR 17′ or N; and

R 14′ , R 15′ , R 16′ and R 17′ are each independently hydrogen; deuterium; a linear or branched, substituted or unsubstituted alkyl radical having 1 to 20 carbon atoms, optionally interrupted by at least one heteroatom selected from O, S and N; a substituted or unsubstituted cycloalkyl radical having 3 to 18 carbon atoms; a substituted or unsubstituted heterocycloalkyl radical interrupted by at least one heteroatom, selected from O, S and N, and having 3 to 18 carbon atoms and/or heteroatoms; a substituted or unsubstituted aryl radical having 6 to 30 carbon atoms; or a substituted or unsubstituted heteroaryl radical interrupted by at least one heteroatom, selected from O, S and N and having a total of 5 to 30 carbon atoms and/or heteroatoms; or

R 14′ and R 15′ , R 15′ and R 16′ , or R 16′ and R 17′ may form together with the carbon atoms to which they are bonded, a saturated or unsaturated or aromatic, optionally substituted ring, which is optionally interrupted by at least one heteroatom, selected from O, S and N, has a total of from 5 to 18 carbon atoms and/or heteroatoms, and may optionally be fused to at least one further optionally substituted saturated or unsaturated or aromatic ring, optionally interrupted by at least one heteroatom, selected from O, S and N, and having a total of from 5 to 18 carbon atoms and/or heteroatoms; or

if A 9′ is CR 12′ , R 12′ and R 17′ together may form a saturated or unsaturated, linear or branched bridge optionally comprising heteroatoms, selected from O, S and N, to which is optionally fused a substituted or unsubstituted, 5- to 8-membered ring comprising carbon atoms and/or heteroatoms selected from O, S and N, and which are optionally substituted with aromatic units, or heteroaromatic units

wherein each substituent is independently selected from the group consisting of a C 1 -C 18 alkyl group, which can optionally be substituted by E and/or interrupted by D; a C 3 -C 12 cycloalkyl group, which can optionally be substituted by G; a C 3 -C 10 heterocycloalkyl radical which is interrupted by at least one of O, S and NR 65 and/or substituted by E; a C 6 -C 14 aryl group, which can optionally be substituted by G; a C 2 -C 30 heteroaryl group, which can optionally be substituted by G; a halogen atom; a fluoroC 1 -C 4 alkyl group; CN; or SiR 80 R 81 R 82 ;

wherein in formula (C):

D 1 is at each independent occurrence CR 34′″ or N;

W is C or N;

E 1 is at each independent occurrence CR 35′″ , N, NR 36′″ or O;

l is 1 or 2;

R 34′″ , R 35′″ , and R 36′″ are each independently hydrogen; substituted, unsubstituted, or branched alkyl; substituted, unsubstituted aryl; or substituted or unsubstituted heteroaryl; or

in each case two R 34′ ″, R 35′″ , or R 36′″ radicals together form a fused ring which may optionally comprise at least one heteroatom selected from O, S and N;

where the dotted line means an optional bridge between one of the D groups and one of the E groups; where the bridge may be defined as follows: alkylene, arylene, heteroarylene, alkynylene, alkenylene, N R38′″ , O, S, SiR 41′″ , R 42′″ , and (CR 43′″ R 44′″ ) v , where one or more nonadjacent (CR 43′″ R 44′″ ) groups may be replaced by NR 38′″ , O, S, SiR 41′″ R 42′″ , where v is 2, 3, 4, 5, 6, 7, 8, 9 or 10; and R 38′″ , R 41′″ , R 42′″ , R 43′″ , and R 44′″ are each hydrogen; alkyl; aryl; or heteroaryl

wherein each substituent is independently selected from the group consisting of a C 1 -C 8 alkyl group; a C 6 -C 14 aryl group, which is optionally substituted with one or more C 1 -C 5 alkyl groups; and a C 3 -C 12 cycloalkyl group;

R is a group of formula

R′ is hydrogen, a C 1 -C 5 alkyl group, or a fluoroC 1 -C 4 alkyl group;

R 1 is hydrogen, a C 1 -C 5 alkyl group, a fluoroC 1 -C 4 alkyl group, or a C 3 -C 6 cycloalkyl group;

R 2 is hydrogen, a C 1 -C 5 alkyl group, a fluoroC 1 -C 4 alkyl group, or a C 3 -C 6 cycloalkyl group;

R 3 , R 3′ and R 3″ are independently of each other hydrogen; a C 1 -C 18 alkyl group, which can optionally be substituted by E and/or interrupted by D; a C 3 -C 12 cycloalkyl group, which can optionally be substituted by G; a C 3 -C 10 heterocycloalkyl radical which is interrupted by at least one of O, S and NR 65 and/or substituted by E; a C 6 -C 14 aryl group, which can optionally be substituted by G; a C 2 -C 30 heteroaryl group, which can optionally be substituted by G; a halogen atom; CF 3 ; CN; or SiR 80 R 81 R 82 ;

R 3 and R 3′ , or R 1 and R 3′ together form a group of formula

 wherein X is O, S, NR 75 or CR 73 R 74 ;

R 4 , R 4′ and R 5 are independently of each other hydrogen; a C 1 -C 18 alkyl group, which can optionally be substituted by E and/or interrupted by D; a C 3 -C 12 cycloalkyl group, which can optionally be substituted by G; a C 3 -C 10 heterocycloalkyl radical which is interrupted by at least one of O, S and NR 65 and/or substituted by E; a C 6 -C 14 aryl group, which can optionally be substituted by G; a C 2 -C 30 heteroaryl group, which can optionally be substituted by G; a halogen atom; CF 3 ; CN; or SiR 80 R 81 R 82 ; or

R 4 and R 4′ together form a group of formula

R 6 and R 7 are independently of each other hydrogen; a C 1 -C 8 alkyl group, optionally interrupted by at least one heteroatom selected from —O—, —S— and —NR 65 —, optionally bearing at least one substituent, which is selected from the group consisting of C 1 -C 8 alkyl, C 1 -C 8 alkoxy, halogen, and C 1 -C 8 haloalkyl, a C 3 -C 6 cycloalkyl group, optionally bearing at least one substituent, which is selected from the group consisting of C 1 -C 8 alkyl, C 1 -C 8 alkoxy, halogen, and C 1 -C 8 haloalkyl; a heteroC 3 -C 6 cycloalkyl group, interrupted by at least one heteroatom selected from —O—, —S— and —NR 65 —, optionally bearing at least one substituent, which is selected from the group consistiong of C 1 -C 8 alkyl, C 1 -C 8 alkoxy, halogen, and C 1 -C 8 haloalkyl; or a C 6 -C 14 aryl group, which can optionally be substituted by one, or two C 1 -C 8 alkyl groups; or

R 6 and R 7 form together a ring

 wherein A 21 , A 21′ ; A 22 , A 22′ , A 23 , A 23′ , A 24′ and A 24 are independently of each other hydrogen, a C 1 -C 4 alkyl group, a C 3 -C 6 cycloalkyl group, a fluoroC 1 -C 4 alkyl group;

D is —CO—, —COO—, —S—, —SO—, —SO 2 —, —O—, —NR 65 —, —SiR 70 R 71 —, —POR 72 —, —CR 63 ═CR 64 —, or —C≡C—;

E is —OR 69 , —SR 69 , —NR 65 R 66 , —COR 68 , —COOR 67 , —CONR 65 R 66 , —CN, or F;

G is E; or a C 1 -C 18 alkyl group; a C 6 -C 14 aryl group, which is optionally substituted by a substituent selected from the group consisting of F, C 1 -C 18 alkyl, which is optionally substituted by F and C 1 -C 18 alkyl, which is interrupted by O; a C 2 -C 10 heteroaryl group; or a C 2 -C 10 heteroaryl group, which is substituted by a substituent selected from the group consisting of F, C 1 -C 18 alkyl,which is optionally substituted by F, SiR 80 R 81 R 82 , and C 1 -C 18 alkyl, which is interrupted by O;

R 63 and R 64 are independently of each other hydrogen; a C 6 -C 18 aryl group, which is optionally substituted by a substituent selected from the group consisting of C 1 -C 18 alkyl, and C 1 -C 18 alkoxy; or a C 1 -C 18 alkyl group, which is optionally interrupted by —O—;

R 65 and R 66 are independently of each other a C 6 -C 18 aryl group, which is optionally substituted by a substituent selected from the froup consisting of C 1 -C 18 alkyl and C 1 -C 18 alkoxy; or a C 1 -C 18 alkyl group, which is optionally interrupted by —O—; or

R 65 and R 66 together form 5-membered ring or 6-membered ring;

R 67 is a C 6 -C 18 aryl group, which is optionally substituted by a substituent selected from the group consisting of C 1 -C 18 alkyl, and C 1 -C 18 alkoxy; or a C 1 -C 18 alkyl group, which is optionally interrupted by —O—,

R 68 is hydrogen; a C 6 -C 18 aryl group, which is optionally substituted by a substituent selected from the group consisting of C 1 -C 18 alkyl and C 1 -C 18 alkoxy; or a C 1 -C 18 alkyl group, which is optionally interrupted by —O—;

R 69 is a C 6 -C 18 aryl group, which is optionally substituted by a substituent selected from the group consisting of C 1 -C 18 alkyl and C 1 -C 18 alkoxy; or a C 1 -C 18 alkyl group, which h is optionally interrupted by —O—;

R 70 and R 71 are independently of each other a C 1 -C 18 alkyl group; or a C 6 -C 18 aryl group, which is optionally substituted by C 1 -C 18 alkyl; and

R 72 is a C 1 -C 18 alkyl group; or a C 6 -C 18 aryl group, which is optionally substituted by C 1 -C 18 alkyl;

R 73 and R 74 are independently of each other hydrogen; a C 1 -C 25 alkyl group, which is optionally interrupted by —O—; a C 7 -C 25 arylalkyl group; a C 6 -C 24 aryl group, which is optionally substituted by C 1 -C 18 alkyl; or a C 2 -C 20 heteroaryl group, which is optionally substituted by C 1 -C 18 alkyl; or

R 73 and R 74 together form a 5-membered or 6-membered ring, which is optionally substituted by a C 1 -C 18 alkyl group, which is optionally interrupted by —O—,or

R 73 and R 74 together form a group of formula ═CR 76 R 77 , wherein

R 76 and R 77 are independently of each other hydrogen; a C 1 -C 18 alkyl group, which is optionally interrupted by O; a C 6 -C 24 aryl group, which is optionally substituted by C 1 -C 18 alkyl; or a C 2 -C 20 heteroaryl group, which is optionally substituted by C 1 -C 18 alkyl; or

R 75 is a C 6 -C 18 aryl group which is optionally substituted by a substituent selected from the group consisting of C 1 -C 18 alkyl and C 1 -C 18 alkoxy; or a C 1 -C 18 alkyl group, which is optionally interrupted by —O—; and

R 80 , R 81 and R 82 are independently of each other a C 1 -C 25 alkyl group, which is optionally interrupted by —O—; a C 6 -C 14 aryl group, which is optionally substituted by C 1 -C 18 alkyl; or a C 2 -C 10 heteroaryl group, which is optionally substituted by C 1 -C 18 alkyl.

2. The metal-carbene complex according to claim 1 , which is a metal-carbene complex of formula (II):

wherein

R is a group of formula

 and

R′ is hydrogen; or a C 1 -C 5 alkyl group.

3. The metal complex according to claim 1 , which is a metal-carbene complex of formula (IIa), formula (IIb), or formula (IIc):

R is a group of formula

 and

R 6 in formula (IIa) is a C 1 -C 8 alkyl group, optionally interrupted by at least one heteroatom selected from —O—, —S— and —NR 65 —, optionally bearing at least one substituent, which is selected from the group consisting of C 1 -C 8 alkyl, C 1 -C 8 alkoxy, halogen, and C 1 -C 8 haloalkyl; a C 3 -C 6 cycloalkyl group, optionally bearing at least one substituent, which is selected from the group consisting of C 1 -C 8 alkyl, C 1 -C 8 alkoxy, halogen, and C 1 -C 8 haloalkyl; a heteroC 3 -C 6 cycloalkyl group, interrupted by at least one heteroatom selected from —O—, —S— and —NR 65 —, optionally bearing at least one substituent, which is selected from C 1 -C 8 alkyl, C 1 -C 8 alkoxy, C 1 -C 8 alkoxy, halogen, and C 1 -C 8 haloalkyl; or

R 6 in formula (IIa) is a group of formula

 wherein:

(i) R 22 , and R 23 and R 24 are independently of each other a hydrogen, or a C 1 -C 5 alkyl group, with the proviso that only one or two of R 22 , R 23 and R 24 may be a C 1 -C 5 alkyl group; or

(ii) R 25 , R 26 and R 27 are independently of each other a hydrogen, or a C 1 -C 5 alkyl group, with the proviso that only one or two of R 25 , R 26 and R 27 may be a C 1 -C 5 alkyl group; or

R 6 and R 7 in formula (IIc) form together a ring

4. The metal-carbene complex according to claim 1 , which is a metal-carbene complex of formula (IVa), formula (IVb), formula (IVc). or formula (IVd):

wherein

m is 1, 2, or 3,

o is 0, 1, or 2; and

the sum of m and o is 3;

X is O, or S;

R 1 is hydrogen, a C 1 -C 5alkyl group, a cyclopentyl group, or a cyclohexyl group;

R 2 is hydrogen, a C 1 -C 5alkyl group, a cyclopentyl group, or a cyclohexyl group;

R 3 is hydrogen, a C 1 -C 5alkyl group, a cyclopentyl group, or a cyclohexyl group;

R 4 and R 5 are independently hydrogen, a C 1 -C 5alkyl group, a cyclopentyl group, or a cyclohexyl group.

5. The metal-carbene complex according to claim 4 , wherein R 4 and R 5 are hydrogen.

6. The metal-carbene complex according to claim 1 which is a metel-carbene complex of formula (IIIa), formula (IIIb), or formula (IIIc):

wherein

R 1 and R 2 are independently of each other a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3 is hydrogen, a C 1 -C 4 alkyl group, or a group of formula

 wherein

R 10 is hydrogen, or a C 1 -C 5 alkyl group;

R 11 is hydrogen, or a C 1 -C 5 alkyl group;

R 12 is a C 1 -C 5 alkyl group; and

R 12′ is a C 1 -C 5 alkyl group; or

wherein

R 2 is CF 3 , a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

R 3 is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3′ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

with the proviso that if either of R 3 and R 3′ is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen; or

wherein

R 3 is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group, or a cyclohexyl group;

R 3′ is hydrogen, especially a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3″ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

with the proviso that if either of R 3 and R 3′ is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen;

and with the further proviso that if either of R 3″ and R 3 is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen;

m is 1, or 2;

o is 1 or 2; and

the sum of m and o is 3;

L is a group of formula (X-1), (X-2), (X-3), (X-4), (X-5), (X-6), (X-7), (X-8), (X-9), (X-10), (X-11), (X-12), (X-13), (X-14), (X-15), (X-16), (X-17), (X-18), (X-19), (X-20), (X-21), (X-22), (X-23), (X-24), (X-25), (X-26), or (X-27)

R 4 and R 5 are independently of each other hydrogen, or a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 6 and R 7 are independently of each other hydrogen, a C 1 -C 8 alkyl group, or a C 3 -C 6 cycloalkyl group; or

R 6 and R 7 form together a ring

 with the proviso that if either of R 6 and R 7 is a C 1 -C 8 alkyl group, or a C 3 -C 6 cycloalkyl group, then the other is hydrogen.

7. The metal-carbene complex according to claim 1 , which is a metal-carbene complex of formula (IIId), formula (IIIe), or formula (IIIf):

wherein

R 1 and R 2 are independently of each other a C 1 -C 5 alkyl group; a cyclopentyl group or a or cyclohexyl group;

R 3 is hydrogen, a C 1 -C 4 alkyl group, or a group of formula

 wherein

R 10 is hydrogen, or a C 1 -C 5 alkyl group;

R 11 is a C 1 -C 5 alkyl group;

R 12 is a C 1 -C 5 alkyl group; and

R 12′ a C 1 -C 5 alkyl group; or

wherein

R 2 is hydrogen, CF 3 , a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

R 3 is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3′ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

with the proviso that if either of R 3 and R 3′ is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen; or

wherein

R 3 is hydrogen, or a C 1 -C 5 alkyl group; and

R 3′ is hydrogen, a C 1 -C 5 alkyl group; a cyclopentyl group or a cyclohexyl group; and

R 3″ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

with the proviso that if either of R 3 and R 3′ is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen; and with the further proviso that if either of R 3″ and R 3 is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen.

8. The metal-carbene complex according to claim 1 , which is a metal-carbene complex of formula (IIIa-1), formula (IIIb-1), formula (IIIc-1), formula (IIId-1), formula (IIIe-1), or formula (IIIf-1):

wherein

R 1 and R 2 are independently of each other a C 1 -C 5 alkyl group; and

R 3 is hydrogen, or a C 1 -C 4 alkyl group; or

wherein

R 2 is CF 3 , a C 1 -C 5 alkyl group; a cyclopentyl group or a cyclohexyl group;

R 3 is hydrogen, a C 1 -C 5 alkyl group; a cyclopentyl group or a cyclohexyl group; and

R 3′ is hydrogen, a C 1 -C 5 alkyl group; a cyclopentyl group or a cyclohexyl group;

with the proviso that if either of R 3 and R 3′ is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen; or

wherein

R 3 is hydrogen, a C 1 -C 5 alkyl group;

R 3′ is hydrogen, or a C 1 -C 5 alkyl group; and

R 3″ is hydrogen, or a C 1 -C 5 alkyl group;

with the proviso that if both R 3′ and R 3″ are independently a C 1 -C 5 alkyl group then R 3 is hydrogen; or

wherein

R 1 and R 2 are independently of each other a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3 is hydrogen, or a C 1 -C 4 alkyl group; or

wherein

R 2 is CF 3 , a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

R 3 is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3′ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

with the proviso that if either of R 3 and R 3′ is a cyclopentyl group or a cyclohexyl group, then the other is hydrogen; or

wherein

R 3 is hydrogen, or a C 1 -C 5 alkyl group;

R 3′ is hydrogen, or a C 1 -C 5 alkyl group;

R 3″ is hydrogen, or a C 1 -C 5 alkyl group;

R 4 is hydrogen, or a C 1 -C 5 alkyl group;

R 5 is hydrogen, or a C 1 -C 5 alkyl group;

with the proviso that if both R 3′ and R 3″ are independently a C 1 -C 5 alkyl group, then R 3 is hydrogen.

9. The meta-carbene complex according to claim 1 , wherein L is

10. The metal-carbene complex according to claim 1 , wherein L is formula (D′):

which is different from formula (D)

wherein

Z 1 and Z 2 are independently of each other N; or

Z 1 and Z 2 are independently of each other CH;

R* is R′;

R 54 is R 4 ;

R 54′ is R 4′ ;

R 55 is R 5 ;

R 56 is 6 ; and

R 57 is R 7 ;

wherein each group R is the same within one metal-carbene complex.

11. The metal-carbene complex according to claim 1 , wherein:

R is a group of formula

 wherein

R 1 and R 2 are independently of each other a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3 is hydrogen, a C 1 -C 5 alkyl group, a group of formula

 wherein

R 10 is hydrogen, or a C 1 -C 5 alkyl group;

R 11 is hydrogen H, or a C 1 -C 5 alkyl group;

R 12 is a C 1 -C 5 alkyl group; and

R 12′ is a C 1 -C 5 alkyl group.

12. The metal-carbene complex according to claim 1 , wherein

R is a group of formula

 wherein

R 2 is a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

R 3 is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3′ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

with the proviso that in case one of R 3 and R 3′ is a cyclopentyl or cyclohexyl group, the other is hydrogen.

13. The metal-carbene complex according to claim 1 , wherein

R is a group of formula

 wherein

R 3 is hydrogen, or a C 1 -C 5 alkyl group; and

R 3′ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group; and

R 3″ is hydrogen, a C 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group;

with the proviso that if both R 3′ and R 3″ are independently a 1 -C 5 alkyl group, a cyclopentyl group or a cyclohexyl group, then R 3 is hydrogen.

14. The metal-carbene complex according to claim 1 , wherein

(i) R 4 is hydrogen, or a C 1 -C 5 alkyl group;

R 4′ is hydrogen; and

R 5 is hydrogen, or a C 1 -C 5 alkyl group; or

(ii) R 4 is hydrogen, or a C 1 -C 5 alkyl group;

R 4′ is a group of

 wherein

R 20 is hydrogen, or a C 1 -C 5 alkyl group;

R 21 is hydrogen, or a C 1 -C 5 alkyl group;

R 22 is a C 1 -C 5 alkyl group; and

R 22′ is a C 1 -C 5 alkyl group; and

R 5 is hydrogen, or a C 1 -C 5 alkyl group; or

(iii) R 4 is hydrogen;

R 4′ is a group of formula

 wherein

R 22 and R 22′ are independently a C 1 -C 5 alkyl group; and

R 5 is hydrogen.

15. The metal-carbene complex according to claim 1 , wherein

(i) R 4 is hydrogen;

R 4′ is hydrogen, or a C 1 -C 5 alkyl group; and

R 5 is hydrogen, or C 1 -C 5 alkyl group; or

(ii) R 4 is hydrogen;

R 4′ is hydrogen; and

R 5 is a group of formula

 wherein

R 20 is hydrogen, or a C 1 -C 5 alkyl group;

R 21 is hydrogen, or a C 1 -C 5 alkyl group;

R 22 is a C 1 -C 5 alkyl group; and

R 22′ is a C 1 -C 5 alkyl group.

16. The metal-corbene complex according to claim 1 , wherein

R 6 and R 7 are independently of each other hydrogen, a C 1 -C 5 alkyl group,or a C 3 -C 6 cycloalkyl group; or

R 6 and R 7 form together a ring

 with the proviso that if one of R 6 and R 7 is a C 3 -C 6 cycloalkyl group, the other is hydrogen.

17. An organic electronic device comprising at least one metal-carbene complex according to claim 1 .

18. A light-emitting layer comprising at least one metal-carbene complex according to claim 1 .

19. An apparatus selected from the group consisting of a stationary visual display unit, an illumination, information panel, a mobile visual display unit, an illumination unit, a keyboard, an item of clothing, a piece of furniture and a wallpaper comprising the organic electronic device according to claim 17 , or the emitting layer according to claim 18 .

20. An apparatus selected from the group consisting of an electrophotographic photoreceptor, a photoelectric converter, an organic solar cell a switching element, an organic light emitting field effect transistor, an image sensor, a dye laser and an electroluminescent device comprising the metal-complex according to claim 1 .

21. A process for preparing a metal-carbene complex of the formula (I) according to claim 1

wherein:

m is 3; and

M, R, R′, R 4 , R 4′ , R 5 , R 6 and R 7 are as defined in claim 1 ;

which process comprises:

reacting a compound of formula (X):

wherein:

X 1 is Cl, Br or I; and

m, M, R′, R 4 , R 4′ , R 5 , R 6 and R 7 are as defined in claim 1 ;

with a compound of the formula:

wherein

Y is:

(a) —B(OH) 2 , —B(OY 1 ) 2 ,

 wherein:

each Y 1 is independently a C 1 -C 10 alkyl group;

Y 2 is a C 2 -C 10 alkylene group;

Y 13 is hydrogen or a C 1 -C 10 alkyl group; and

Y 14 is hydrogen or a C 1 -C 10 alkyl group;

(b) —SnR 307 R 308 R 309 , wherein:

R 307 , R 308 and R 309 are independently hydrogen or C 1 -C 6 alkyl, wherein two C 1 -C 6 alkyl radicals may optionally form a common ring;

(c) —ZnR 310 R 311 , wherein:

R 310 is halogen; and

R 311 is a C 1 -C 10 alkyl group, a C 6 -C 12 aryl group or a C 2 -C 10 alkenyl group; or

(d) —SiR 312 R 313 R 314 , wherein:

R 312 , R 313 and R 314 are independently halogen or a C 1 -C 6 alkyl group; and

R 1 , R 2 , R 3 , R 3′ and R 3″ are as defined in claim 1 .

22. The process according to claim 21 , which process comprises:

reacting a compound of formula (XI):

wherein:

m, M, R′, R 4 , R 4′ , R 5 , R 6 and R 7 are as defined in claim 21 ;

with a halogenating agent selected from the group consisting of chlorine, bromine, iodine, chlorine fluoride, bromine fluoride, iodine fluoride, bromine chloride, iodine chloride, iodine bromide, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate), N-chloroacetamide, N-bromoacetamide, N-iodoacetamide, N-chloropropionamide, N-bromopropionamide, N-iodopropionamide, N-chlorobenzamide, N-bromobenzamide, N-iodobenzamide, N-chlorosuccinimide, N-bromosuccinimide, N-iodosuccinimide, N-chlorophthalimide, N-bromophthalimide, N-iodophthalimide, 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, 1,3-diiodo-5,5-dimethylhydantoin, benzenesulfo-N-dibromamide, chloramine B and chloramine T;

to obtain a compound of formula (X):